1. Field
The presently disclosed subject matter relates to a manufacturing method of semiconductor light emitting/detecting devices including LEDs, laser diodes, photodiodes, phototransistors, etc. and to the devices themselves. More specifically, the subject matter relates to the manufacturing method of semiconductor light emitting/detecting devices that include a structure that provides secure mounting on conductor patterns, and to the associated devices themselves.
2. Description of the Related Art
FIG. 6 shows a conventional LED device 90 that is a surface mount chip type by way of example of typical semiconductor light emitting devices. The LED device includes a light emitting layer of p-n junction formed between p-type layer 91 and n-type layer 92. An electrode portion 93 is formed on the p-type layer and an electrode portion 94 is formed on the n-type layer.
The conventional LED device is provided with solder coating layer 95p, 95n on the respective electrode portions 93, 94. A resin coating layer is formed on a surrounding surface except for the electrode portions in order to provide damp proofing measures.
When the conventional semiconductor light emitting device based upon the above structure is mounted on a circuit board, the conventional device is placed on a pair of conductor patterns 81p and 81n that are formed on a circuit board 80. The conventional device is fixed with an adhesive 82 between the bottom surface thereof and the circuit board, if necessary. The circuit board in such state is passed through a reflow furnace, etc., and is heated to a temperature that is more than a melting temperature of solder.
In the above process, the solders of solder coating layers 95p, 95n on the respective electrode portions 93, 94, are melted, caused to flow down, and are diffused on the conductor patterns 81p and 81n of the circuit board, as shown in FIG. 7. The solders are solidified in a normal or ambient temperature after the circuit board has passed through the reflow furnace. Thus, the conventional LED device is electrically connected and is mechanically fixed between the electrode portion 93 and the conductor pattern 81p, and between the electrode portion 94 and the conductor pattern 81n. The exemplary conventional LED device of surface mount chip type can be electrically connected and mechanically fixed as described in further detail, for example, in Japanese Patent No. 3,022,049 (corresponding to Japanese Patent Application No. JP-6-326365 A) and its English translation, which are hereby incorporated in their entirety by reference.
In the conventional semiconductor light emitting device of surface mount chip type described above, electrical and physical contact occurs only between a thickness portion of the electrode portions 93 (94) and the conductor patterns 81p (81n). The connective strength between the conventional device and the circuit board mainly depends on the solder portions 95p (95n) that cover a portion of the electrode portions 93 (94) and the conductor patterns 81p (81n), so that the contact area between the bottom thickness portions of the electrode portion 93 (94) and the conductor patterns 81p (81n) is very narrow and small.
Thus, a big difference in connective strengths for conventional devices can easily be caused by several variables, including temperature of the reflow furnace, thickness of the solder coated on the electrode portions 93 (94), soldering compatibility with the conductor pattern 81p (81n), and other conditions. Recently, in equipment that is required to resist extreme vibration and impact, such as vehicles, ships, aircraft, etc., the use of LED devices has increased with the goal/purpose of improving reliability, efficiency, etc. Under these circumstances, the use of the conventional surface mount chip type semiconductor light emitting devices has various problems, and big differences in the connective strength may be caused by different conditions at the time of production as described above.
Luminous energy of the semiconductor light emitting device can be influenced by the amount of open surface and the number of the chips being used. The conventional LED device 90 has another problem in that the device is completely closed by the two surfaces of the electrode portions 93, 94 making the device 90 appear darker than a “dome shaped” LED device in which the same chip thereof is mounted on one lead frame via die bonding, for example.
The disclosed subject matter has been devised to consider the above and other problems and characteristics. Thus, an embodiment of the disclosed subject matter can include manufacturing methods and associated semiconductor light emitting/detecting devices that do not cause the above-described various problems related to differences in the connective strength caused during production, and to reduce or change other associated problems and characteristics of the conventional methods and devices.